1. Field of the Invention
The present invention relates to an SNMP (Simple Network Management Protocol), and more particularly, to a method for controlling trap generation of an SNMP.
2. Description of the Background Art
One of network management protocols for a communication network management, the SNMP defines a control structure for a management-object resource (an object) on the basis of an RFC 1157 standard.
FIG. 1 shows a construction of a manager and an agent adopting an SNMP in accordance with a conventional art.
As shown in FIG. 1, the SNMP is adopted in the communication network consisting of a central SNMP management system (manager) 10 and at least one SNMP management-object system (agent) 12.
The manager 10 serves to control a management-object resource (object) of the agent 12 through the SNMP. That is, the manager 10 outputs an object access message (GET/SET/GETNEXT) to the agent 12 and performs searching, changing, generating or deleting on the object defined in an MIB (Managed Information Base) of the agent 12.
The GET message is a message to read a data from the MIB 14, and the SET message is a message to write a data in the MIB 14. The GETNEXT message is a message to read an object next to the object read by the GET message. A GETResponse is a message to transmit the data read from the MIB 14 to the manager 10 according to the GET/GETNEXT message.
Accordingly, when the manager 10 searches information, it transmits an OID (Object ID) together with the object access message (GET/GETNEXT) to the agent 12, and the agent 12 transmits the GETResponse message including a value of the corresponding data together with the OID back to the manager 10. In this respect, the OID is the ID of the object, and every data is discriminated by the OID.
The SNMP supports a ‘Trap’ operation so that the agent 12 voluntarily transmits information on the object to the manager 10, without depending on the request of the manager 10.
Describing a management object behavior, access authorization and grammar structure allowable for the object existing in the MIB 14, the SNMP defines a trap in the MIB 14 by relating an object to be subjected to trap generation to a condition of the trap generation. The trap is defined as follows:    ObjectName TRAP-TYPE    ENTERPRISE {enterprise name}    VARIABLES {variable name}    DESCRIPTION “comment”    ::=Sub OIDAccordingly, when the state (i.e., system up/down and system disturbance) of the object is changed, the agent 12 voluntarily outputs a TRAP PDU (Protocol Data Unit) to inform the manager 10 of the state change of the object. In this respect, the TRAP PDU includes an OID and a corresponding data value.
The network management protocol through the SNMP will now be described in detail.
The manager 10 outputs an ID of the object (OID) together with the GET message to the agent 12 in order to search the state of the object of the agent 12. At this time, the OID is an ID of each object, by which every management-objected data is discriminated.
Upon receipt of the GET request, the agent 12 reads a data value from the MIB 14 and transmits the GETResponse message to the manager 10. The GETResponse message includes a pair of an OID and a read data (OID and a read data) form.
The manager 10 outputs the next OID together with the GETNEXT message in order to search the next object, and in response, the manager 12 transmits the GETResponse message in the same form to the MANAGER 10. This operation is repeatedly performed so as for the manager 10 to search the state of the every object.
When the manager 10 writes a data in the MIB 14, it outputs an OID of the object and a SET message, and the agent searches a target data by using the OID and changes a corresponding data value.
Meanwhile, unlike the GET/GETNEXT/SET message, the trap management behavior is used for the agent 12 voluntarily report the state of the object periodically. That is, after the agent 12 relates a specific data and a trap generation condition, when it comes to a predetermined cycle, the agent 12 outputs a trap PDU Protocol Data Unit) to inform the manger 10 of the change in the state of the object. Also, the TRAP PDU consists of a pair of an OID and a data, the same as that of the GETResponse message.
However, in the SNMP standard-based MIB technique of the conventional art, the object to be subjected to the trap generation is statically defined. Accordingly, conventionally, since the trap operation is adoptable only to the object defined in the MIB, the manager is not able to add or delete a specific object as an object as necessary during the network management operation.
In addition, once a trap condition is defined in the MIB, a trap operation is applied to every defined object, resulting in that the agent generates a TRAP PDU even for a object with little state change.
Thus, the agent generates a trap more than necessary and thus the manager should process numerous TRAP PDU transmitted from the plurality of agents, so that the traffic is increased. This works as a factor to degrade the management efficiency in the management network using the SNMP